The use of a sophisticated high-speed camera and associated image intensifier and optical relay system will be used in the detailed visualization of tear film thickness changes during the blinking process. In addition, this system will allow the examination of lid motion abnormalities, corneal wetting problems, and tear spreading dynamics during blinking. This data will be used in the formation of a comprehensive theory of corneal wetting and the tear film formation process, and provide for the development and in vivo evaluation of artificial tear preparations. In particular, it is planned to: (1) determine the dynamic changes in tear film thickness and its distribution during the actual blinking process in normal and dry-eyed subjects; (2) examine in detail abnormal blink motions and corneal wetting problems in dry eye patients; (3) correlate abnormal blink patterns and poor corneal wetting with observed corneal pathology; and (4) to the extent possible, correct or favorably alter abnormal blink and corneal wetting characteristics by blink training, lid manipulation, and the instillation of "tailor-made" artificial tear preparations.